Devices for heating filaments or treads



April-14,1970 H. ISCHIPPERSI ETAL v3,506,304

DEVICESFOR HEATING FILAMENTS OR TREADS Filed March 8. 196'? 2 Sheets-Sheet 1 FIG.2 FIG?) F|G,4 AC'i'UAL D ES\IRED 1235 k k H T a. r-IZ E I I2 g j z i t 0c k TEMPERATURE 36 36 PRIOR ART PRIOR ART INVENTORSI HEINZ SCHIPPERS HANS LOHEST- HEINZ TREPTOW ATT'YS April 14, 1970' H. SCHIPPERS ETAL DEVICES FOR HEATING FILAMEN'I'S OR TREADS Filed March '8. 1967 2 Sheets-Sheet 2 FIGS FIG.6

I INVENTORS'. HEINZ SCHIPPERS HANS LOHEST HEINZ TREPTOW United States Patent "ice 3,506,804 DEVICES FOR HEATING FILAMENTS 0R TREADS Heinz Schippers and Hans Lohest, Remscheid-Lennep,

and Heinz Treptow, Ennepetal-Milspe, Germany, assiguors to Barmag Barmer Maschinenfabrik Aktiengesellschaft, Wuppertal, Germany Filed Mar. 8, 1967, Ser. No. 621,566 Claims priority, application Germany, Mar. 14, 1966, B 86,192 Int. Cl. F27b 9/ 06' US. Cl. 219-388 9 Claims ABSTRACT OF THE DISCLOSURE Elongated, filament heating devices heated by, or in form of, electric resistors with varying area and/or transverse cross section for maintaining substantially constant or predetermined, varied temperature throughout length of heating device.

BACKGROUND OF THE INVENTION The manufacture and after treatment of synthetic polymer filaments or threads is often required for a stretching or texturing of the running filaments or threads, which are heated to a certain temperature. Many different devices have been suggested in the past for this purpose. Known heating devices were made as plates rails, pipes or the like and are heated by an electrical current which passes through them. The thread touches either a long curved area or runs without touching at a short distance along a flat heating area.

Also known are devices which incorporate a curved surface which comes in contact with the thread and which is mounted transversely on a pipe. A heating fluid flows through this pipe and heats the surface to increase the temperature in the direction of the thread passage. The temperature course is further influenced by variation of the cross section and/or area of the heating element along the thread passage.

In all these arrangements it has been difficult to heat the thread equally across its cross section at a high thread velocity. This is desirable for obtaining the necessary plasticity in the after treatments. The thread also should not be overheated in some areas since the thread material disintegrates at too high temperatures. The required tolerable lower temperature and tolerable upper temperature are often close together. Therefore, in order to obtain a good plasticity of the thread it is necessary to keep the thread velocity low. Economic reasons required higher velocities, which, however, were possible only by elongation of the heating surface.

Measurements on electrically heated surfaces have shown that only about half of the heating elements length reaches the desired temperature, while at the beginning and end of the heating length the surface temperature is considerably below the desired level, therefore only about 50% of the length of the heating surface is effective.

For this reason it has been suggested to equalize the temperature course along the entire length of the heating length by use of a multiple layer heating plate. This plate consists primarily of two plates such as silver or copper electrodes, which serve as current conductors to and from the electrical heating element. Between them, the specific electrical resistance increases with a higher temperature. These elements have a light Weight, are very expensive and work very sluggishly, and therefore do not eliminate the danger of a local overheating or cooling.

The basic objective of the invention herein is to provide an electrical heating device with an instantly heated, heat transfer surface with more uniform surface temperature in the direction of the thread passage so that the desired temperature is obtained over substantially the entire length of the heating erea and within the tolerable temperature variations. This is achieved by variable heat generation in individual areas of the heating element by change of the electrical resistance in these areas.

In one of the simpler forms of the invention, the transverse cross section of the electrical resistance element along the longitudinal axis (in the direction of the thread passage) changes in the different areas of the heating body in such a way that the actual temperature course is independent of externally influenced heat losses and is held nearly constant over the length of the thread passage or follows another predetermined course. The transverse cross section of the heat generating resistor element, therefore, has to be smaller in areas where a higher heat energy input is required.

Ohms law explains the relation between voltage U; resistance R; and current I in the formula:

is valid:

By substitution of U in the Formula 2 by the right portion in Formula 1 we have:

The electrical resistance of the individual heating elements along the lingth of the passage is different because of the different cross sections and therefore the Equation 3 should contain the sum of the individual values R +R +R instead of just R, where x represents the number of cross sections of the heating elements. A voltage drop occurs in the individual cross sections of the elements; this is identified by AU AU AU the sum of all AU is equal to the applied voltage U. The three equations mentioned above are also valid for the individual cross section of the heating element and (3) can be written in the form:

A cross section change and therefore electrical resistance change at the place x of the heating element can therefore change the heating output at this place. However, it has to be noted that for example an increase in the resistance R also increases the total 'resistance R. So the current I according to Equation 1 has to decrease and the heating output W according to (2) decreases, a constant voltage U being assumed. A cross sectional change at one place of the heating element therefore effects the entire temperature course over the length of the heating element. Accordingly, a control resistor has to be connected in parallel for the adjustment of the current, or in series connection for the adjustment of the total voltage U when a certain level and course of the temperature is to be adjusted to suit a certain heating curve. A machine such as a stretch twisting machine or a crimping machine consists of a number of different working stations and has as many heating elements so that equal working conditions can be adjusted at all stations. The above mentioned concepts relate, as stated, to direct current but can be applied to alternating current.

With adevice according to this invention it is possible to fix the temperature course in such a way that it follows a certain curve. A cooling zone that might be required for a process can be incorporated.

Heating elements are usually made of sheet metal of 0.1 to 1 mm. thickness and they are mounted on brackets which are shaped to suit the elements. The bracket is insulated against current passage or is made of an insulating material itself. A bent heating rail can for example be made of thin steel sheet metal which can be bonded to a correspondingly curved surface of an aluminum bracket of severalcentimeters in thickness and which can be insulated against current passage by application of a fine anodized layer. It is also possible to mount the heating rail in heat proof fire brick material, in such a case the support has not only the purpose of support for the thin heating element but also, if heated by the element, will equalize additional large temperature differences of small heating length increments. Such temperature differences occur at sudden cross section changes on the heating element. The support provides a smoothening effect upon the course of the temperature curve.

BRIEF DESCRIPTION OF THE INVENTION The invention herein embodies heating elements of relatively high electrical resistance, which elements become heated upon passage of electric current therethrough. The surface temperature along the entire length of the elongated heating elements is made more uniform or is varied within relative uniform limits with the requirements of the thread heat treatment by the variation of the transverse cross section of the heating elements, particularly at opposite ends thereof. This cross section change can be obtained by a change in width and/or thickness of the resistor element, or by machining, e.g., drilling 'holes in its area. Another possible cross section change may be effected by the arrangement of additional current conducting joints between the individual areas of the electrical resistor element.

The invention can also be used in so-called multiple systems where, for example, two like curved heating surfaces are opposite one another with their concave sides" in opposition. They may both have the same or different temperatures or the same or different transverse cross sectional changes. It is also possible to arrange a pulley at the entry and exit end of the plate pair. One or both pulleys can be driven and both of their circumferences may be partially covered by the plates. It is of advantage to arrange the plates on, or with their support members on, a swivel and use them as winders feeler and shut off means.

The described devices can also be of a design that does not have current flow directly through the heating element, but utilize eddy currents to do the required heating.

To reduce radiation heat losses or to obtain a certain chimney effect, the heating element may be enclosed within a housing. This housing can comprise an entrant slot for the thread.

Finally, the heating element can be equipped with a thread guiding device which determines the passage of the thread and even possibly keeps it at a certain distance from the heating surface.

DESCRIPTION OF THE DRAWINGS tion of one preferred form of an elongated heating element of the invention.

FIG. is a front elevation of another embodiment. FIG. 6 is a side elevation of a further embodiment. FIGS. 7 and 8, respectively, are perspective views of additional embodiments; and

FIG. 9 is a side elevation of a thread heating unit with two opposed heating plates.

4 DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a known, elongated, longitudinally curved heating plate 10 in a front View. The thread l'lll'lS thereover in the direction of the arrow and is shown in a dashdot-dash line. FIG. 2 shows the temperature curve of a heating length of a device like that in FIG. 1, the thread running from the bottom to the top. The desired temperature is indicated in the diagram as a straight line. The actual temperature course is shown in a curved line, and approaches the desired course in the center portion only so that a considerable part of the heating length is unused or ineffective. Corresponding equally unfavorable heating area temperatures can be observed with flat or tubelike heating elements.

FIGS. 3 and 4 show an embodiment of this invention. The longitudinally curved heating plate 12 is heated by an electric current that passes directly through the plate and has an electrical resistance that changes with an increasing or decreasing cross section along the path of the thread, so that the actual temperature course along the path of the thread corresponds about to the desired value of FIG. 2. The cross sectional change is here by increase or decrease of the plate width only. Such change is effected by the tapered, lower segment 13 and the shorter, tapered, upper segment 11.

Such a cross sectional change can also be facilitated by holes 14 in the edge of the heating plate 15, as iS shown in FIG. 5. Otherwise the plate 15 has a rectangular shape and is longitudinally curved. The distance between the bores increases with the direction of the thread movement thereacross in the lower segment 16 and then decreases in the upper segment 17. The required cross sectional change can also be effected by solid joinder with one or several current conducting plates 18, on a heating plate 19. This design is shown in FIG. 6.

The heating body may also consist of a tube 20, which optionally may have a longitudinal slot 21 for insertion or removal of the thread, as shown in FIG. 7. The tube 20 may be bent longitudinally to provide a curved contact area. The heating element of this design often has a favorable chimney effect.

A construction of special advantage is shown in FIG. 8. The heating element 22 comprises a very thin steel sheet 23 of a 0.1 to 0.3 mm. thickness. The cross sectional change according to this invention is done by change in width of sheet 23. The sheet 23 is bonded on a support member 24 of aluminum or another material. The support member 24 is insulated against the heating element 22 by an anodized layer 32 in order to prevent a current passage through the member 24.

FIG. 9 shows a double heating plate system. The two longitudinally curved heating plates 25 and 26 oppose one another with their convex sides facing outwardly and are mounted on a support arm 27. The support arm 27 is mounted on a shaft 28 so it can swivel. The pair of plates 25, 26 cover the directional pulleys 29 and 30 to some extent with a narrow spacing. One or both pulleys can be driven. The support arm 27 is so arranged that it may be pushed out of its operational position and trips a micro switch 31 which shuts the drive oif. The support arm 27 is held by the spring 33 and the stop 34 to assure the operational position.

The thread T passes longitudinally across the longitudinally convex surface of the thread-heating elements shown in FIGURES 3-8. Contact between the heated surface and the thread passing thereover is maintained by passing the thread through suitable guide means such as thread guide eyes 35 and 36 located at opposite longitudinal ends of the heating elements.

An example will show the decided economic advantages of the invention. It was possible to draw a thread of 70 den. at a velocity of meter/minute over a longitudinally curved heating plate of common chromiumnickel steel. The heating rail was 1000 mm. long, 0.3 mm. v thick and had a constant width of 25 mm. The actual temperature curve is shown in FIG. 2. The desired temperature was 190 C. It was possible to obtain the desired 190 C. temperature over 90% of the heating element length by tapering of the entrant end to 19 mm. width from a 25 mm. width over a length of 600 mm. in a straight line. The exit end was tapered to 22 mm. width. This taper started at the 850 mm. length where it was 25 mm. This change gave the thread a more complete heating, and it was possible to run the thread at a velocity of 180 meter/minute.

The devices according to this invention are not only useful for heat treatment of synthetic polymer fibers, but also for use with threadlike products, for their stretching and texturing, such as threads of thermoplastic materials which are called strings, multiple component strips, hollow threads, etc.

It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the invention, or sacrificing any of its'attendant advantages, the forms herein disclosed being preferred embodiments for the purpose of illustrating the invention.

The invention is hereby claimed as follows:

1. A device for the heating of filaments, thread or thread-like articles which comprises an elongated electrical resistance element having longitudinally bowed, convex thread-contacting surface, electrical connections at opposite longitudinal ends thereof for passing current through said element, means for guiding a filament in longitudinal passage across said convex surface with said filament in contact with said surface, and said element having a transverse cross section varying along the length of said element to provide changes in electrical resistance in said element along its length in the direction of the thread running thereover in the following sequence: first, a decreasing resistance, then a constant resistance, and then an increasing resistance; thereby providing control of the temperature of said surface compensating for uneven external heat losses from said element and also providing a substantially constant or predetermined variable temperature of said surface along its length.

2. A device as claimed in claim 1 wherein said heating element is a longitudinally bowed plate of high electrical resistance, said plate tapering from its longitudinal midportion toward opposite longitudinal ends thereof.

3. A device as claimed in claim 1, said element being a longitudinally bowed plate of high electrical resistance with plurality of holes at predetermined spacings along opposite longitudinal edges thereof to effect said varying transverse cross section.

4. A device as claimed in claim 1 wherein said element is an elongated, longitudinally bowed plate of high electrical resistance having at least one longitudinally bowed plate of shorter length secured to the undersurface of the longitudinal midportion of said first mentioned plate in electrical-conducting contact with said first mentioned plate.

5. A device as claimed in claim 1, said electrical resistance element being a thin sheet of metal of a thickness of 0.1 to 1 mm., and a support member supporting said sheet of metal in heat and electrical insulating relationship therewith.

6. A device as claimed in claim 1 wherein said element is a longitudinally bowed tube with a longitudinal slot therein extending from end to end of said tube.

7. A device as claimed in claim 1, a pair of said longitudinally bowed heating elements being supported on a common support member with the respective longitudinally convex, thread-contacting surfaces thereof facing oppositely outwardly, a rotatable, filament guiding pulley between each respective end of said pair of elements, and the longitudinal ends of said elements extending partially over said pulleys.

8. A device as claimed in claim 1, a pair of said 1ongitudinally bowed heating elements being supported on a common support member with the respective longitudinally convex, thread-contacting surfaces thereof facing oppositely outwardly, a rotatable, filament guiding pulley between each respectiveend of said pair of elements, the longitudinal ends of said elements extending partially over said pulleys, means mounting said support for swivel movement, and electrical switch means operable by swiveling of said support.

9. A device as claimed in claim 1, wherein the width and/or thickness of said element varies to effect said varying transverse cross section.

References Cited UNITED STATES PATENTS 3,382,555 5/1968 Smoots 219-388 2,780,047 2/ 1957 Vandamme et al 219-388 2,596,327 5/1952 Cox et al 338-217 3,336,558 8/1967 Wright 338-217 B. A. GILHEANY, Primary Examiner D. M. MORGAN, Assistant Examiner US. Cl. X.R. 338-217 In the drawings: sheets 1 and 2, in the title, "TREADS" should zg g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N1). 1506,80 1 Dated Ap il 1 1970 Inventor(s) Heinz Schippers et a1 It is certified that erronappears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

read -'-'-THREADS In the specification: Column 1, line 2, "TREADS" should read THREADS Column 2, line 4, "erea" should read area line 52, "lingth" should read length mum AN SEALED 06f 6 I Anesa Edward 1!. Fletcher, Jr.

Ammi mm 3- JR. L. 0mm eomiasionow 0: Patents 

